The invention relates generally to systems for inspecting porous substrates.
Porous substrates, such as cellulose and cotton matrices (e.g. 31 ETF, FTA and FTA elute cards available from Whatman) are often used to store biological samples, such as blood. In addition to forensic uses, a new application area for these cards is in the pharmaceutical industry, which is using them to store dried blood samples from pharmacokinetic and toxicokinetic studies. Sensitivity, accuracy and consistency has become even more important. To achieve the necessary quality requirements for these applications, the quality and consistency of the porous substrate is essential.
The porous substrate material is typically manufactured in rolls and then cut into pieces. As shown in FIG. 1, currently, the quality of the paper is checked by a person who manually drops a sample liquid onto the paper with a pipette and then manually quantifies the rate at which the liquid was absorbed by the paper. The measurements used to quantify the rate of absorption are taken by a person who manually measures a given spot of liquid with calipers multiple times over a period of time as the spot expands. This method is slow, tedious and subject to error throughout the manual process of spotting the paper, measuring the spot with calipers over time using a stopwatch as it expands and then calculating the rate of expansion based on the measurements over time. The rate of expansion is typically calculated manually by a technician and then entered into a log, or the measurement data is manually entered into a system and calculated by the system.
As such, there exists a need for an automated method and system for inspecting porous substrates during the manufacturing process. More specifically, there is a need for methods and systems that are able to consistently quantify the characteristics and quality of porous substrates.